PCI: don't shrink bridge resources

When clearing leaf bridge resources, trying to get a big enough one, we
could shrink the bridge if there is no resource under it.  Confirm
against the old resource side to make sure we're increasing the
allocation.
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/setup-bus.c

@@ -382,7 +382,7 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size)
 {
 	struct pci_dev *dev;
 	struct resource *b_res = find_free_bus_resource(bus, IORESOURCE_IO);
-	unsigned long size = 0, size1 = 0;
+	unsigned long size = 0, size1 = 0, old_size;
 
 	if (!b_res)
  		return;
@@ -407,12 +407,17 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size)
 	}
 	if (size < min_size)
 		size = min_size;
+	old_size = resource_size(b_res);
+	if (old_size == 1)
+		old_size = 0;
 /* To be fixed in 2.5: we should have sort of HAVE_ISA
    flag in the struct pci_bus. */
 #if defined(CONFIG_ISA) || defined(CONFIG_EISA)
 	size = (size & 0xff) + ((size & ~0xffUL) << 2);
 #endif
 	size = ALIGN(size + size1, 4096);
+	if (size < old_size)
+		size = old_size;
 	if (!size) {
 		if (b_res->start || b_res->end)
 			dev_info(&bus->self->dev, "disabling bridge window "
@@ -433,7 +438,7 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
 			 unsigned long type, resource_size_t min_size)
 {
 	struct pci_dev *dev;
-	resource_size_t min_align, align, size;
+	resource_size_t min_align, align, size, old_size;
 	resource_size_t aligns[12];	/* Alignments from 1Mb to 2Gb */
 	int order, max_order;
 	struct resource *b_res = find_free_bus_resource(bus, type);
@@ -483,6 +488,11 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
 	}
 	if (size < min_size)
 		size = min_size;
+	old_size = resource_size(b_res);
+	if (old_size == 1)
+		old_size = 0;
+	if (size < old_size)
+		size = old_size;
 
 	align = 0;
 	min_align = 0;